On MacOS, I can hold the Control key to turn on snapping. However I believe that the Command key should be used instead, or at least an option should be given to the user to choose whether the use Control or Command for snapping. This is because:
The Windows’ Ctrl key’s equivalent in Mac is the Command key, not the Control key (Ctrl+C = Command+C, Ctrl+V = Command+V). Therefore, as Ctrl is used for activating the snapping mode in Windows, its equivalent (Command key) should be used in Mac.
If I wanted to save a file in Windows Blender, I press Ctrl+S. If I wanted to undo an action, I hit Ctrl+Z. If I wanted to turn on snapping, I hold Ctrl. However, in Mac Blender, I hit Command+S for saving, Command+Z for undo, but Control for snapping. It is inconsistent.
I work extensively with both platforms and it’s more complicated than you think. There’s no direct equivalent for modifier keys, the philosophy and history between platforms is a bit different.
Besides this, it’s incredibly easy to customize the keymap in Blender to fit your wishes.
Personally; Snapping is a Blender function, while saving, copying, pasting etc are more OS functions used across most apps. I don’t think holding cmd for snapping makes much sense.
Default keymap files contain only “CTRL”, and “CMD” is added by the “platform_helpers.py” script when the keymap loading. The script is looking for ‘CTRL’ but ‘LEFT_CTRL’ and ‘RIGHT_CTRL’ is assigned for snapping, so the script just doesn’t see snapping items and does not add CMD-version for them.